[Wien] Spin-orbit coupling SCF not converging

[Laurence Marks]

For the convergence, please run "Check-mixing" (for recent versions) and
paste the result. This may give an idea. It may be that the calculation is
slowly changing the spin/orbital momentum and progressing towards the
solution. You may have a tunnel or even spiral convergence.

For SOC, the accuracy depends upon the number of bands used (nband with
ELPA). I suggest testing the convergence with a smaller problem (e.g. bulk
MoS2) then transferring this to your problem, e.g. chose nband such that it
gives states to the same energy above Ef.

_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu

On Tue, Nov 26, 2019, 07:21 Luigi Maduro - TNW <L.A.Maduro at tudelft.nl>
wrote:

> Hello there WIEN2k users,
>
>
>
> I am having a convergence problem with a supercell calculation of a slab
> of MoS2 including Spin-Orbit Coupling (SOC). The supercell is made by
> cutting in the plane of MoS2 which leads to either only edge Mo atoms or
> edge S atoms. A vacuum parallel to the edges is introduced (about 18
> angstroms) that separates the repeating images. Converged SCF calculations
> without SOC were found with this type of geometry for various widths. These
> converged SCF calculations were then used as input for an SCF calculation
> with SOC for the different widths. However, when including SOC only the
> smallest width gave a converged SCF calculation, albeit after doubling the
> amount of k-points and increasing nbands(more than twice what was
> originally suggested when running init_so). The larger widths do not result
> in a converged SCF calculation, even after substantially increasing nbands.
> Is the solution to just keep on increasing the amount of k-points until I
> do get converged SCF calculations or is the inclusion of the vacuum giving
> problems for lapwso?
>
>
>
>
>
> As a side not, I have a general question on how to relate Emax and nbands
> in case.in1. Up until recently I have been using SCALAPACK in WIEN2k and
> now I have switched to using ELPA. In the case of MoS2, a system with large
> spin-orbit coupling, the userguide recommends to increase the value of Emax
> to up to 10 Ry for large SOC systems when running the init_so script. If
> one is using ELPA then nbands should be increased. In the case of ELPA
> should nbands be increased to twice the amount given in case.in1 when
> initially running init_so?
>
>
>
>
>
> PhD candidate
> Kavli Institute of Nanoscience
>
> Department of Quantum Nanoscience
>
> Faculty of Applied Sciences
>
> Delft University of Technology
>
>
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